Introducer sheath for the placement of a stent at the ostium of an artery

ABSTRACT

Disclosed is an ostial stent positioner that has the form of a wire for most of its length and having a short cylinder with expandable legs situated at the positioner&#39;s distal end. The cylinder with its attached wire acts as an introducer sheath to introduce a stent delivery system with a stent into the artery that is to be stented. A second aspect of the present invention is a method for accurately placing a stent at the ostium of an artery that would have an ostial stenosis. Examples of such arteries that have ostial stenoses are the right and left main coronary arteries, a saphenous vein graft as used in coronary bypass surgery and the renal arteries. Also disclosed are designs for the short cylinder that have a variable diameter so as to fit snugly within guiding catheters having different inside diameters.

REFERENCE TO A PREVIOUS PATENT APPLICATION

This is a continuation-in-part application of the patent applicationSer. No. 11/388,161 filed on Mar. 24, 2006.

FIELD OF USE

This invention is in the field of devices for placing stents within astenosis that extends to or near the ostium of an artery.

BACKGROUND OF THE INVENTION

Although most stenoses do not occur at the ostium of an artery, thereare thousands of cases each month where the mouth of an artery (theostium) is substantially obstructed at its aortic take-off; this iscalled an aorto-ostial lesion. In such cases, the interventionalcardiologist or radiologist is frequently unable to place the stent'sproximal end within ±2 mm of the ostial plane. Two types of incorrectstent positions are (1) when the stent's proximal end extends more than2 mm into the aorta, and (2) when the stent's proximal end is placedmore than 1-2 mm into the artery distal to the ostial plane.

In U.S. Pat. No. 6,458,151, F. S. Saltiel describes an ostial stentpositioning device. However, the most important feature of such adevice; namely, and expandable distal portion that touches the wall ofthe aorta near the ostium of the artery to be stented is not optimizedfor easy usage of such a device. Furthermore, the Saltiel design isessentially a cylindrical sheath within the guiding catheter whichsheath extends for the entire length of the guiding catheter. Such adesign would have an incredible amount of friction between thecylindrical sheath and the interior wall of the guiding catheter whichwould make it very difficult to operate. In addition, the Saltiel designwould substantially obstruct the internal cross-section of the guidingcatheter along its entire length, limiting the injection of contrastmaterial, and the passage of guide wires, balloon catheters, and/orstents.

In U.S. Pat. No. 5,749,890, A. Shaknovich utilizes a stent mounted on acatheter that has an inflatable section that touches the wall of theaorta in the vicinity of the ostium of the artery that is to be stented.Such a design precludes an accurate stent positioning system that can beused with the stent delivery system of any manufacturer.

SUMMARY OF THE INVENTION

A first aspect of the present invention is an ostial stent positionerthat has the form of a wire for most of its length and having a shortcylinder with expandable legs situated at the positioner's distal end.The cylinder with its attached wire acts as an introducer sheath tointroduce a stent delivery system with a stent into the artery that isto be stented. A second aspect of the present invention is a method foraccurately placing a stent at the ostium of an artery that would have anostial stenosis. Examples of such arteries that have ostial stenoses arethe right and left main coronary arteries, a saphenous vein graft asused in coronary bypass surgery and the renal arteries. Each of thesearteries has an ostium situated at the aorta.

The preferred method for using this invention would be to firstback-load the ostial stent positioner within a guiding catheter. A guidewire could then be loaded through the guiding catheter, and through thepre-deployed ostial positioning system that had already been placedwithin the guiding catheter. The guiding catheter would be advanced overthe guide wire into the aorta. The next action would be to place theguiding catheter through the aorta in a conventional manner so that itsdistal end will be engaged within or near the ostium of the artery thatis to be stented. The guide wire would then be advanced through theguiding catheter until its distal end was placed distal to the stenosis.If pre-dilitation of the ostial stenosis was needed, a balloonangioplasty catheter would be advanced over the guide wire and throughthe guiding catheter and the catheter's balloon would be inflated topre-dilate the stenosis. After the balloon angioplasty catheter wasremoved from the guiding catheter (or if no pre-dilatation was required)then a stent delivery system with the appropriately sized stent would beadvanced over the guide wire until the stent's proximal end lay at ordistal to the ostium of the artery. The stent delivery system wouldtypically have its proximal radiopaque marker band placed distal to theostial plane of the artery to be stented. While retaining the guide wireand a distal portion of the stent delivery system in the artery, theguiding catheter with the positioner inside would then be pulled back ashort distance into the aorta. The positioner would then be advanceduntil its expandable legs at the positioner's distal end extended beyondthe guiding catheter's distal end, thus allowing the expandable legs toexpand. The guiding catheter would then be advanced until its distal endsurface pushes gently against the positioner's expandable legs to engagethe legs against the wall of the aorta and generally align the legs atthe ostium of the artery that is to be stented. The plane of the “feet”which are located at the distal ends of the expandable legs, would thenbe situated at the artery's ostial plane, and with a leg-to-leg diameterthat is larger than the diameter of the artery to be stented. Since theexpandable legs would have feet that would be formed from a materialthat included a radiopaque substance or from a metal that is coated withor made from a radiopaque metal, the interventional cardiologist who isperforming this procedure would have a clear angiographic/fluoroscopicmarker of the ostial plane of the artery that is to have a stent placedwithin the ostial stenosis of that artery. The interventionalcardiologist would then pull the stent delivery system back until theproximal radiopaque marker band within the balloon of the stent deliverysystem was aligned appropriately relative to the radiopaque feet of theexpandable legs. The balloon would then be inflated to deliver the stentaccurately at the ostial stenosis with the stent's proximal end lyingwithin 2 mm of the ostial plane of the artery (typically just proximalto the true ostial plane). It is expected that an experiencedinterventional cardiologist could place the proximal end of the stentwithin 1.0 mm and just proximal to the ostial plane.

In a prior application one embodiment of this invention was describedthat requires a separate introducer device that is used to place thepositioner into the guiding catheter. This continuation-in-partapplication teaches an improved embodiment of the invention that allowsthe sheath-like ostial stent positioner to be placed into the guidingcatheter without requiring a separate introducer device.

The main object of this invention is to describe a means for accuratelyplacing the proximal end of a stent within ±2 mm of the ostial plane ofan artery that has a stenosis located at or near the ostium of thatartery.

Another object of this invention is to place the proximal end of a stentwithin ±1.0 mm of the ostial plane of an artery that has a stenosislocated at or near the artery's ostium.

Still another object of the present invention is to teach a method foraccurately placing a stent within an ostial stenosis.

Still another object of the present invention is to utilize a short slitcylinder to which expandable legs are connected, which slit cylinderslides easily within a guiding catheter.

Still another object of the present invention is to utilize a variablediameter cylinder to which the expandable legs are connected, whichvariable diameter cylinder is designed to expand radially outward so asto create gentle contact between the cylinder's outer surface and theinterior surface of the guiding catheter.

These and other objects and advantages of this invention will becomeobvious to a person of ordinary skill in this art upon reading thedetailed description of this invention including the associated drawingsas presented herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a Touhy-Borst fitting, a guiding catheter andan ostial stent positioner that acts as an introducer sheath for placingthe proximal end of a stent in close proximity to the ostial plane of anartery that has an ostial stenosis.

FIG. 2 is a longitudinal cross section of a distal portion of the ostialstent positioner located within the guiding catheter showing theexpandable legs in their folded state.

FIG. 3 is a cross section of the distal portions of the guidingcatheter, a stent on a stent delivery system and the positioner showingthe distal end plane of the feet of the expandable legs placed at theostial plane of an artery having an ostial stenosis.

FIG. 4 is a top view of an alternate embodiment of the present inventionusing a slit cylinder with expandable legs.

FIG. 5 is an end view of the embodiment of FIG. 4.

FIG. 6 is the side view of the embodiment of FIG. 4.

FIG. 7 is a perspective view of an alternative embodiment of theinvention using a helical coil cylinder for improved flexibility.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a side view of a catheter system 10 whose object is toaccurately place a stent with its proximal end being situated close tothe ostial plane of an artery having an ostial stenosis. The cathetersystem 10 includes the guiding catheter 40 and an ostial stentpositioner 17 that has a wire 11 which connects a small diameter handle12 to a cylinder 16 (shown in FIG. 2) which has expandable distal endlegs 14 with radiopaque feet 15. The guiding catheter 40 that has aproximal Luer fitting 41 that is joined to a Touhy-Borst fitting 30.When the feet 15 are fully expanded, the diameter “D” would typically bebetween 4 and 10 mm for coronary artery stenting and between 5 and 15 mmfor stenting a renal artery. When the expandable legs 14 with radiopaquefeet 15 are fully expanded they would have the general appearance of thepetals of a flower. When the legs 15 are pushed forward beyond thedistal end of the guiding catheter 40, they expand radially outward asshown in FIG. 1. When the handle 12 is pulled back, the legs 15 areretracted into the guiding catheter 40 and then the positioner 17 can bepulled out of the guiding catheter 40 after the stent has been placedinto the ostial stenosis.

The Touhy-Borst fitting 30 has an adjustable seal fitting 31 (which is ahemostasis valve) that can initially be slightly loosened to allow thepositioner 17 to be advanced or pulled back through the guiding catheter40 without excessive blood leakage. When the expandable legs 14 are intheir correct position for placement at the ostial plane of a stenosedartery, (as seen in FIG. 3) the adjustable seal fitting 31 can betightened to hold a fixed position of the legs 23 relative to theguiding catheter 40 during stent deployment. The Luer fitting 32, beingin fluid communication with the lumen of the guiding catheter 40, can beused for flushing the lumen with saline solution and/or for injectingcontrast medium. The Luer connector 33 is used to form a removablefluidic seal with the Luer fitting 41 of the guiding catheter 40.

FIG. 2 is an enlarged cross section of the distal portions of theguiding catheter 40 and the positioner 17. The positioner 17 is shownwith its expandable legs 14 in their unexpanded state within the guidingcatheter 40. In this state, the guiding catheter 40 can be advancedthrough an introducer sheath at the patient's groin until its distal endis within the ostium of the artery that is to be stented. Furthermore,in this state, both a guide wire and a stent delivery system can beadvanced through the guiding catheter 40 and positioner 17 and throughthe ostial stenosis. The fixed diameter cylinder 16 is attached at itsproximal end to the wire 11 and at its distal end to each of the fourlegs 14. Although 3 legs 14 (of an actual 4 legs) are shown in FIG. 2,as few as 2 or as many as 16 of petal-like legs 14 could be used for aneffective array of expandable legs 14.

FIG. 3 is a cross section of a distal portion of the catheter system 10shown with the distal plane 45 of the radiopaque feet 15 placed at theostial plane of a stenosed artery. The feet 15 are attached to theexpandable legs 14 that are attached to the cylinder 16 which has itsposition within the guiding catheter 40 adjusted by means of the wire11. Any such placement of the feet 15 can be defined as having theirdistal plane 45 “co-planar” with the ostial plane of the artery that hasan ostial stenosis. FIG. 3 also shows a guide wire 26 placed through thestent delivery system 20 which has a shaft 21, a proximal radiopaquemarker band 24, a distal radiopaque marker band 25 and a stent 23mounted onto a balloon 22. The ostial stent positioner 17 would bedesigned to introduce essentially any commercially available stentdelivery system 20 into an arterial stenosis. Thus, any interventionalcardiologist could use the positioner 17 with any stent delivery systemthat he or she favors. FIG. 3 also shows how the guiding catheter 40 canbe used to gently push the feet 15 against the wall of the aorta at theostium of the stenosed artery. It is also possible to push the feet 15against the wall of the aorta by pushing the positioner 17 in a distaldirection without the assistance of the guiding catheter 40.

At the start of the stenting procedure, the ostial stent positioner 17would be positioned as shown in FIG. 2 with the expandable legs 14placed inside the guiding catheter 40. The catheter system 10 and theguide wire 11 could then be advanced through a conventional introducersheath (not shown) typically placed at the groin of the patient intowhom the stent 23 is to be placed. The guide wire 26 (or a separate0.035 inch diameter guide wire) would be placed into and through theostial stenosis and the guiding catheter 40 would be advanced until itsdistal tip was placed through the arterial ostium. The stent deliverysystem 20 would then be advanced over the guide wire 26 and through theguiding catheter 40 and positioner 17 until the proximal radiopaquemarker band 24 was positioned just distal to the ostium of the stenosedartery. The guiding catheter 40 would then be pulled back into theaorta. The positioner 17 (which was already back loaded into the guidingcatheter 40) would then be advanced through the guiding catheter 40until the expandable legs 14 extended out of the distal end of theguiding catheter 40. The guiding catheter 40 would then be pushed gentlyforward in a distal direction so as to obtain the configuration asgenerally shown in FIG. 3.

With the configuration as shown in FIG. 3, the interventionalcardiologist would be able to clearly visualize the distal plane 45 ofthe radiopaque feet 15 and also visualize the proximal radiopaque markerband 24. When the radiopaque marker band 24 is pulled backward until itis co-planar with feet 15, then the proximal end of the stent 23 wouldbe placed within ±2 mm of the plane of the ostium of the vessel which isto be stented. The balloon 22 would then be inflated to deliver thestent 23 into the ostial stenosis. Thus, an interventional cardiologistshould be able to readily place the proximal end of the stent 23 within±2 mm of the ostial plane. With some experience, it is expected that theproximal end of the stent 23 could be placed within at least ±1.0 mm ofthe ostial plane and probably within ±0.5 mm. The optimum placement ofthe proximal end of the stent 23 is that it extends approximately 0.5 mminto the lumen of the aorta.

Although one method for accurately placing the stent 23 into an ostialstenosis has been described herein, it should be understood that thereare several other ways that the present invention could be used toprovide accurate stent positioning within an ostial stenosis. Forexample, the guiding catheter 40 with the positioner 17 in place asshown in FIG. 2 could first be placed over a 0.035 inch diameter guidewire and into the lumen of the ostial stenosis. That larger diameterguide wire could then be removed and a 0.014 inch diameter guide wirecould be placed through the stenosis. The stent delivery system 20 couldthen be advanced over that guide wire 26 and positioned as shown in FIG.3. The guiding catheter could then be pulled back and the expandablelegs 14 could then be deployed as described herein. An important featureof the system 10 is that the guiding catheter 40 and positioner 17 couldbe held to be motionless while the guide wire 26 or the stent deliverysystem 20 could be advanced forward or pulled back to obtain an accuratepositioning of the stent 23 within the ostial stenosis.

FIGS. 4, 5 and 6 illustrate an alternative embodiment ostial stentpositioner 50 utilizing a slit cylinder 56 that would replace the fixeddiameter cylinder 16 of FIGS. 2 and 3. The slit cylinder 56 is designedto join to a wire 51 that is equivalent to the wire 11 of FIGS. 1, 2 and3, which wire 51 is used to move the ostial stent positioner 50 withinthe guiding catheter 40. The wire 11 of FIGS. 1, 2 and 3 was aconventional small diameter, round wire. The wire 51 of FIGS. 4 and 6 isa flat wire. It should be understood that the term “wire” shall includeany structure whose cross section is round or a small diameter cylinderor a flat wire or a wire whose cross section is an arc of a circle thatis less than 270 degrees. The attachment of the wire 51 to the slitcylinder 56 can be by means of welding, soldering or (with a somewhatdifferent configuration) by means of a biocompatible adhesive. It isalso conceived that the slit cylinder 56 and the wire 51 can be formedfrom a single piece of metal. The slit 57 of the slit cylinder 56provides a spring-like action to allow the slit cylinder 56 to have aslight outward force against the inner wall of the guiding catheter 40.The outside diameter of the slit cylinder 56 when free in air would havea diameter that is slightly larger than the inside diameter of thelargest diameter guiding catheter 40 that would be use for a particularprocedure. But the slit 57 would allow the outside diameter of the slitcylinder 56 to compress to fit into any size guiding catheter that wouldtypically be used for ostial stenting. The slit 57 would have a width“S” that is typically between 0.2 and 1.0 mm. The length “L” of the slitcylinder 56 would typically be between 5 and 10 mm. What is mostimportant is that the length “L” should not be more than 20% as long asthe guiding catheter 40 and ideally the length “L” is less than 1% aslong as the guiding catheter 40. The shorter the length, the less willbe the frictional force against the interior wall of the guidingcatheter 40. The ideal material for the slit cylinder 56 is a shapememory alloy and the ideal shape memory alloy would be Super ElasticNitinol.

As seen in FIGS. 4, 5 and 6, the expandable legs 54 with radiopaque feet55 are joined to slit cylinder 56. The feet 55 (as well as other partsof the ostial stent positioner 50) could be made radiopaque by platingwith a highly radiopaque metal such as platinum, gold or tantalum orthey could be made from a high density metal. An important feature ofthe ostial stent positioner 50 is that the angle “A” of the slitcylinder 56 as shown in FIG. 6 is approximately 20 degrees and certainlyless than 30 degrees. This small angle allows the ostial stentpositioner 50 to be back loaded into the guiding catheter 40 withoutrequiring a special introducer device as was described in a priorapplication. Furthermore, if the interventional cardiologistaccidentally advances the slit cylinder 56 beyond the distal end of theguiding catheter 40, the ostial stent positioner 50 can be readilypulled back into the guiding catheter 40. Therefore, the designs shownin FIGS. 4, 5, and 6 are an improvement over prior designs because theostial stent positioner 50 is easier to place into the guiding catheter40 without requiring an additional introducer tool and without requiringan additional step in the method for placing a stent at the ostium of anartery.

To introduce a stent delivery system into a coronary artery, the typicaldiameter for the guiding catheter 40 would be 6, 7 or 8 French (Fr). Itwould be highly desirable for the ostial stent positioner 50 to be madewith a single diameter of its slit cylinder 56 that holds the expandablelegs 54. This would decrease the inventory requirements for thepositioner 50 for each catheterization lab that performs coronaryinterventions. Specifically, only one diameter of the slit cylinder 56would be required and it would fit into guiding catheters that areeither 6, 7 or 8 Fr. It would also be highly desirable to have thecylinder 56 (as shown in FIGS. 4, 5 and 6) expand radially outward togently press against the inner surface of the guiding catheter 40. Tohave a single product that would be suitable for 6, 7 or 8 Fr guidingcatheters, the outer diameter of the slit cylinder 56 should beapproximately the inside diameter of an 8 Fr guiding catheter. Such acylinder 56 would then also fit snugly within either 6 Fr or 7 Frguiding catheters. The wall thickness for the slit cylinder 56 wouldideally be between 0.001 and 0.003 inches.

It should also be understood that a larger diameter guiding catheter 40could be used specifically for treating an ostial stenosis in a renalartery. Guiding catheters as large as 14 Fr or as small as 6 Fr could beused for inserting a stent into an ostial stenosis of a renal artery. Ofcourse, the uncompressed diameter of the slit cylinder 56 must also beat least slightly larger than the inside diameter of any such guidingcatheter. Therefore, it should be understood that the dimensions for theslit cylinder 56 should be somewhat larger for renal stenoses ascompared to the dimensions that are optimum for stenoses of the coronaryarteries. However, the length of the slit cylinder 56 of such a ostialstent positioner for stenting a renal ostial stenosis should be lessthan 20% of the length of the guiding catheter.

FIG. 7 is a perspective view of an alternative embodiment of theinvention which is the ostial stent positioner 60. The positioner 60 hasa helical cylindrical body 66 that is quite flexible because of itshelical design. Legs 64 with radiopaque feet 65 are attached at thedistal end of the cylinder 60 and a wire 61 is attached at the proximalend of the cylinder 60. The dimensions and materials for the ostialstent positioner 60 are comparable to the dimensions and materials ofthe ostial stent positioner 50.

The major advantages of the designs of the slit cylinder 56 and thehelical cylinder 66 as compared to the invention of Saltiel are at leasttwo-fold: (1) the cylinders 56 and 66 are very short compared to thelength of the guiding catheter 40 so that they slide easily within theguiding catheter 40; and (2) both the slit cylinder 56 and the helicalcylinder 66 are each radially expandable, variable diameter cylinders soas to gently contact the interior wall of the guiding catheter 40. Theimportant characteristic of the variable diameter cylinder is that itsoutside diameter becomes substantially equal to the inside diameter ofthe guiding catheter into which the variable diameter cylinder isinserted. Two advantages of the variable diameter cylinder are that itallows for one-size-fits-all design to decrease the inventory of theostial stent positioners in any catheterization lab and also, by beinggently expanded against the wall of the guiding catheter 40, thesevariable diameter cylinders 56 and 66 provide the largest interior lumenwhich facilitates the introduction of the stent delivery system. TheSaltiel invention has a fixed diameter cylinder that extends for theentire length of the guiding catheter and therefore a different size ofostial stent positioner would be required for each different diameter ofthe guiding catheter. An additional disadvantage of the Saltielinvention is that the full length cylinder within the guiding catheterwould be very difficult to advance or pull back because the frictionalforces would be very large. In addition, there would be severelimitations for radio-opaque contrast injection through the Saltieldevice due to increased fluid impedance.

An important aspect of the design of the ostial stent positioner is thatit should be coated with a lubricity agent to ease its motion throughthe guiding catheter. Hydrophilic polymers and silicone are examples oflubricity agents that could be used to coat at least part of the ostialstent positioner.

Various other modifications, adaptations and alternative designs are ofcourse possible in light of the teachings as presented herein. Thereforeit should be understood that, while still remaining within the scope andmeaning of the appended claims, this invention could be practiced in amanner other than that which is specifically described herein.

1. In combination a guiding catheter and an introducer sheath type ofostial stent positioner for facilitating the placement by an operator ofthe proximal end of a stent within ±2 mm of the ostial plane of anartery that has an ostial stenosis, the positioner having a wireextending for most of its length that is attached to a cylinder that isplaced within the guiding catheter, the length of the cylinder beingless than 20% of the length of the guiding catheter, the cylinder alsobeing attached to at least two expandable distal legs that end withradiopaque feet that form a distal plane when they are pushed in adistal direction out of the distal end of the guiding catheter andagainst the interior wall of the aorta, the positioner being designedfor placement of the distal plane of the radiopaque feet to besubstantially co-planar with the ostial plane of the artery when theostial stent positioner is urged forward in a distal direction after theexpandable distal legs have been expanded radially outward beyond thedistal end of the guiding catheter.
 2. The combination of claim 1 wherethe guiding catheter has a diameter that lies between 4 Fr and 14 Fr. 3.The combination of claim 1 where the wire has a handle at its proximalend to facilitate the handling of the positioner by the operator.
 4. Thecombination of claim 3 where the handle is formed from a plasticmaterial.
 5. The combination of claim 1 where the expandable legs havefeet that are formed from a radiopaque metal or coated with a radiopaquemetal.
 6. The combination of claim 5 where the feet on the expandablelegs have an outside diameter when expanded that lies between 4 and 15mm.
 7. The combination of claim 1 where the positioner has expandablelegs that are formed from a combination of a plastic material and ametal, the combination being generally radiopaque.
 8. The combination ofclaim 1 where the positioner has expandable legs which are generally inthe shape of a flower that has at least two petals.
 9. The combinationof claim 8 where the positioner's expandable legs have at least fourpetals.
 10. The combination of claim 1 where the cylinder of the ostialstent positioner is of a fixed diameter.
 11. The combination of claim 1where the cylinder of the ostial stent positioner is a variable diametercylinder that is designed to have a diameter that is variable dependingon the inside diameter of the guiding catheter into which the cylinderis inserted, the variable diameter cylinder being designed to exert agentle outward force against the interior wall of the guiding catheter.12. The combination of claim 11 where the variable diameter cylinder isin the form of a helix.
 13. The combination of claim 11 where thevariable diameter cylinder is a slit cylinder.
 14. The combination ofclaim 13 where the slit cylinder that is attached to the expandable legshas an angle where the slit cylinder is joined to the wire that is lessthan 30 degrees.
 15. The combination of claim 11 where the variablediameter cylinder is formed from a shape memory alloy.
 16. Thecombination of claim 15 where the shape memory alloy that is used toform the variable diameter cylinder is Super Elastic Nitinol.
 17. Amethod for placing the proximal end of a stent within an artery that hasan ostial stenosis so that the stent's proximal end is positioned within±2 mm of the artery's ostial plane, the method including the followingsteps: a) placing an introducer sheath type of ostial stent positionerthat has at least two expandable distal legs into a guiding catheterwith the expandable legs in an unexpanded state, the expandable legshaving at least some portion that is radiopaque and the expandable legsbeing attached to a cylinder that is less than 20% as long as the lengthof the guiding catheter; b) causing the expandable legs to expand in aregion beyond the distal end of the guiding catheter; c) urging theostial stent positioner in a forward, distal direction so that a distalplane of the expanded legs is placed substantially co-planar with theostial plane of the artery that has the ostial stenosis; and d)positioning a stent within the stenosis of the artery so that thestent's proximal radiopaque marker band is situated relative to thedistal plane of the expanded legs of the positioner so that the stent'sproximal end is located within ±2 mm of the ostial plane of the arterywhen the stent is deployed.
 18. The method of claim 17 where thepositioner's expanded legs are generally shaped in the form of a flowerwith at least two petals.
 19. The method of claim 17 where the expandedlegs have at least some portion that is formed from a radiopaque metalor coated with a radiopaque metal.
 20. The method of claim 17 where theexpanded legs are attached to a variable diameter cylinder that isformed from shape memory alloy.
 21. The method of claim 20 where boththe expanded legs and the variable diameter cylinder are both formedfrom a shape memory alloy.
 22. The method of claim 17 where the cylinderis a variable diameter cylinder that seeks an outside diameter that issubstantially the same as the inside diameter of the guiding catheterinto which the variable diameter cylinder is inserted.
 23. The method ofclaim 22 where the variable diameter cylinder is a slit cylinder.
 24. Incombination a guiding catheter and an introducer sheath type of ostialstent positioner for facilitating the placement by an operator of theproximal end of a stent within ±2 mm of the ostial plane of an arterythat has an ostial stenosis, the positioner having a wire extending formost of its length that is attached to a variable diameter cylinder thatis placed within the guiding catheter, the outside diameter of thevariable diameter cylinder being substantially the same as the insidediameter of the guiding catheter into which the variable diametercylinder is inserted, the length of the variable diameter cylinder beingless than 20% of the length of the guiding catheter, the variablediameter cylinder also being attached to at least two expandable distallegs that end with radiopaque feet that form a distal plane when theyare pushed in a distal direction out of the distal end of the guidingcatheter and against the interior wall of the aorta, the positionerbeing designed for placement of the distal plane of the radiopaque feetto be substantially co-planar with the ostial plane of the artery whenthe ostial stent positioner is urged forward in a distal direction afterthe expandable distal legs have been expanded radially outward beyondthe distal end of the guiding catheter.
 25. The combination of claim 24where the variable diameter cylinder is a slit cylinder.